This application is based upon Japanese Patent Application Nos. Hei. 11-131701 filed on May 12, 1999, Hei. 11-131702 filed on May 12, 1999, Hei. 11-132866 filed on May 13, 1999, Hei. 11-287346 filed on Oct. 7, 1999, and Hei. 11-287347 filed on Oct. 7, 1999, the contents of which are incorporated herein by reference.
1. Field of the Invention
This invention relates to map display devices, and particular to a map display device for displaying buildings, roads and the like on a screen in a three-dimensional manner. More particularly, the invention relates to a map display device capable of displaying guidance line.
2. Related Art
In vehicular navigation devices as disclosed in, for example, Japanese Patent Laid-Open Nos. Hei 9-171348, Hei 9-62179 and Hei 9-212083, the buildings, roads and the like are displayed on the screen in a three-dimensional manner, so that the user can readily understand the map.
There has further been proposed a device, which enables the altitude of viewing point to be changed at the time of displaying the map in a three-dimensional manner, so that the map can be viewed more desirably. One of the examples can be represented by a vehicular navigation device which, as shown in FIG. 34A, permits the user to select the altitude of viewing point of a bird""s-eye view out of several altitudes (e.g., three altitudes including low, intermediate and high).
In the three-dimensional map display in which buildings are three-dimensionally displayed on the screen, in general, when the viewing point is set to a low altitude, it often happens that the road or building, which the user wishes to see, is not displayed due to being hidden behind high buildings located in front. Conversely, when the viewing point is set to a high altitude, the stereo feeling or the perspective feeling is spoiled due to over lapping among the buildings. Such circumstances vary depending upon the buildings and roads displayed on the screen, their arrangements, topography, a portion of the map which the user wishes to see, etc. According to the above vehicular navigation devices, however, the user is allowed to select the viewing point out of only three altitudes, and is not often allowed to set the viewing point at an optimum altitude to meet various situations. When the altitude of viewing point is changed, further, the display of the screen greatly changes at one time, and the user finds it difficult to grasp a relationship between the display of picture of before being changed and the display of picture of after being changed.
There has further been proposed a vehicular navigation device, which enables the altitude of viewing point to be increased or decreased in many steps each by a predetermined altitude, as shown in FIG. 34B. According to this vehicular navigation device, the user is allowed to set the viewing point to a desired altitude to meet the circumstances on the display of map and objects. However, this vehicular navigation device still involves a difficulty in the operation in that when it is attempted to change the viewing point from a low altitude to a high altitude, the viewing point of a desired altitude is not readily set despite the altitude of the viewing point is successively increased by a predetermined altitude each time by manipulating a switch or the like. However, according to this vehicular navigation device, when the viewing point is set to a relatively high altitude, the map displayed on the screen may change little, despite the altitude of the viewing point is successively increased or decreased by a predetermined altitude each time. As a result, the user does not feel that the viewing point is ascending or descending, despite of manipulating the switch.
On the other hand, when the user sets a destination, the vehicular navigation device calculates an optimum route from the present position to the destination, and displays a route guidance line on the roads on the map that is three-dimensionally displayed. It is further possible to display information related to traffic jam, congestion and vacancy as lines (road information guidance lines) on the roads or outside the roads but along the roads, based upon the road traffic information obtained by the communications among the vehicles on the roads.
FIGS. 35A and 35B illustrate display screens describing a route guidance line in addition to the map that is three-dimensionally drawn. In FIGS. 35A and 35B, a building 1 is drawn as a stereo picture, and a route guidance line 3 (hatched belt portion) is drawn on the road 2. On the practically displayed screen, the whole route guidance line 3 appears in a color (e.g., red) different from the building 1 or the road 2. On the screen of FIG. 35B, the road 2 and the route guidance line 3 are so drawn that the width gradually decreases toward the distance so that a perspective feeling is obtained.
However, when the altitude of viewing point is decreased to nearly the height of a vehicle so as to obtain a display on the screen as viewed by the eyes of a driver in contrast with the screens shown in FIGS. 35A and 35B, then, the feeling of depth of the route guidance line 3 is lost, and it becomes difficult to see the route guidance line ahead of the turning point (ahead of the point turning to the left in FIGS. 35A and 35B).
The route guidance line 3 is drawn after the buildings and roads are three-dimensionally displayed on the screen. When the road 2, on which the route guidance line 3 will be drawn, is hidden by other buildings or roads, and the overlapped portion is not drawn on the road (which is not shown in FIGS. 35A, 35B), the route guidance line 3 is drawn on the buildings and on the roads for the overlapped portion. Accordingly, it becomes difficult to grasp a perspective relationship between the route guidance line 3 and other buildings or roads, or it becomes difficult to recognize the stereo shapes of the other buildings or roads. This inconvenience also happens when the road information guidance lines (e.g., lane guidance lines showing turn to the left, right, or go straight, and traffic jam information guidance lines) are to be displayed.
The map may further display traffic regulations information, such as one-way, speed limit, under construction, no parking, no stop, caution to falling rocks, etc. So far, the traffic regulations information has been drawn by bit map data. However, when the design drawn by bit map data is displayed afar beyond the viewing point in the three-dimensional display, the display of data of a particular sequence is inhibited and the data are thinned out. Conversely, when the above picture is displayed near the viewing point, the data are increased by, for example, tripling the data of each dot.
Therefore, the quality of display inevitably decreases, the design displaying the traffic regulations information becomes less recognizable, and it becomes difficult to watch the map display device during driving the car.
On the other hands, in a navigation device which two-dimensionally displays the map, the names of places and the names of buildings are also displayed by characters at the time of displaying the roads and buildings on the display means. In a navigation device which three-dimensionally displays the roads and buildings of a map, on the other hand, the names of places or the names of buildings are not usually displayed by characters but, instead, such names are displayed by characters when the user designates a desired building or the like.
In this constitution which displays the names of the places or the names of the buildings for each designation, however, it is not easy to comprehend the position of the desired building when the user has approached the destination. Besides, the user must repeat the designation operation many times to display the desired building, which is cumbersome.
This invention was accomplished in view of the above-mentioned circumstances, and has a first object of providing a map display device which, when the buildings and roads are three-dimensionally displayed, imparts perspective feeling to the route guidance lines and to the road information guidance lines so that they can be more favorably watched.
A second object of this invention is to provide a map display device which, when traffic regulations information is three-dimensionally displayed, enhances the quality of display so that they can be more favorably watched.
A third object of this invention is to provide a map display device which, when a map is three-dimensionally displayed, enables the viewing point to be set to a desired altitude maintaining good operability and enables the display on the screen to be smoothly changed accompanying the operation for changing the altitude of the viewing point.
A fourth object of this invention is to provide a map display device which three-dimensionally displays a map while also displaying the names of a plurality of buildings by character through a relatively simple operation.
According to one aspect of the present invention, a display control unit three-dimensionally displays guidance line when a map is three-dimensionally displayed on the screen. Even when the altitude of viewing point is set on the screen to an altitude which is as low as that of a vehicle, the user is allowed to easily recognize the guidance line and to easily grasp a perspective feeling of the buildings and roads.
According to another aspect of the present invention, a display control means displays, in a color different from the colors of other portions, the portions that are hidden behind facilities among the route guidance line when a map is three-dimensionally displayed on the screen. Therefore, the user is allowed to easily recognize the positional relationship among the guidance line and facilities. Besides, the shapes of the facilities are not smeared out by the guidance line, and do not become ambiguous.
According to still another aspect of the present invention, a screen control means finds a proportionally changing altitude by multiplying the present altitude of viewing point by a predetermined ratio of change every time when an altitude-changing instruction is input, and uses, as a new altitude of viewing point, the altitude that is obtained by increasing or decreasing the present altitude of viewing point by the proportionally changing altitude. Therefore, many altitudes of viewing points can be set in response to the input of the altitude-changing instruction. Besides, the amount of change in the altitude of viewing point increases with an increase in the altitude of viewing point, and the user is allowed to favorably set any desired altitude of viewing point.
Further, since the altitude of viewing point changes by a predetermined ratio with respect to the present altitude of viewing point, the user is allowed to gain a feeling of rising viewing point or lowering viewing point on the three-dimensionally displayed map upon the input of an instruction for changing the altitude. By continuously inputting the instruction for changing the altitude, further, the display on the screen can be smoothly changed.
According to far still another aspect of the present invention, it is allowed to select a display on the display unit for also displaying characters telling the names related to a plurality of buildings, or a display which does not display such characters. Therefore, the names of the buildings can be displayed relatively easily without requiring cumbersome designation operation. Besides, the names of the plurality of buildings can be simultaneously displayed instead of a single building.
According to the other aspect of the present invention, it is allowed to select a display for also displaying characters telling the names related to a plurality of buildings in addition to displaying the buildings in a three-dimensional manner but suppressing their height or displaying the buildings in plane shapes, or a display which displays the buildings without changing their height while displaying the characters.